Fuze actuating system

ABSTRACT

An electronic, digital, time fuze, has a time base which is introduced over a radar command link at a rate which is inversely proportional to the desired projectile flight time. A target following ranging device, such as a ranging laser, provides target range information to a pulsed radar transmitter. The range signal from the ranging device controls a variable pulse rate control unit which in turn adjusts the transmitter pulse rate to a value inversely proportional to the target range. The transmitter is fixed to the weapon system and radiates in the direction of the projectile flight path. Each projectile includes a fuze actuating circuit consisting of an antenna, an r.f. detector, a fixed-set counter and a firing circuit. At launch, the fuze actuating circuit within each projectile becomes actuated a short distance after departure from the gun muzzle. As the projectile travels towards its target it receives a series of r.f. pulses at a rate which will just fill the counter when the projectile is at the proper range. The counter within the fuze counts the pulses received during its flight to target. When the fixed-set number has been accumulated, the firing circuit detonates the payload.

United States Patent [1 1 Ziemba Dec. 11, 1973 FUZE ACTUATING SYSTEM[75] Inventor: Richard T. Ziemba, Burlington, Vt.

[731 Assignee: General Electric Company,

Burlington, Vt.

221 Filed: Aug. 3, 1972 211 Appl. No.: 277,562

Related [1.8. Application Data [62] Division of Ser. No. 843,478, July22, 1969, Pat. No.

[52] 0.8. CI 102/70.2 P, 102/80 [51] Int. Cl. F42c 13/04, F42c 15/04,F42c 11/00 [58] Field of Search 102/702 [56] References Cited UNITEDSTATES PATENTS 3,688,701 9/1972 Kern 102/702 P Primary Examiner-BenjaminA. Borchelt Assistant Examiner-Thomas H. Webb Attorney-Bailin L. Kuch eta1.

RANGING I LASAR VARlABLE PULSE RATE CONTROL [57] ABSTRACT An electronic,digital, time fuze, has a time base which is introduced over a radarcommand link at a rate which is inversely proportional to the desiredprojectile flight time. A target following ranging device, such as aranging laser, provides target range information to a pulsed radartransmitter. The range signal from the ranging device controls avariable pulse rate control unit which in turn adjusts the transmitterpulse rate to a value inversely proportional to the target range. Thetransmitter is fixed to the weapon system and radiates in the directionof the projectile flight path. Each projectile includes a fuze actuatingcircuit consisting of an antenna, an r.f. detector, a fixed-set counterand a firing circuit. At launch, the fuze actuating circuit within eachprojectile becomes actuated a short distance after departure from thegun muzzle. As the projectile travels towards its target it receives aseries of r.f. pulses at a rate which will just fill the counter whenthe projectile is at the proper range. The counter within the fuzecounts the pulses received during its flight to target. When thefixed-set number has been accumulated, the firing circuit detonates thepayload.

1 Claim, 7 Drawing Figures TRANSMITTER ANTENNA PULSE RANSM ITTERPMENTEDUEC 1 1 I975 SHEET 1 BF 3 E mm CT ET J N 0 ME RMM P A A T o 2RANSMITTER VARIABLE PULSE RATE CONTROL FIGZ FIG.3

FIRE

I OUINTER RESET RECEIVING ANTENNA DET.

AMR

POWER PATENTEU BEE] 1 ms SHEET 2 BF 3 PATENTEBDEB n ma 3.777.665

sum 3 m 3 TRANSMITTER PULSE RATE (X I000) 00000 00 0 00 wsa gwggggTARGET RANGE(METERS) FUZE ACTUATING SYSTEM This application is adivision of copending U.S. Pat. 3,714,898, filed July 22, 1969 andissued Feb. 6, 1973.

BACKGROUND OF THE INVENTION 1. Field of Art This invention relatesgenerally to fuze actuating systems, and especially to systems whereinthe range adjustment may be varied in flight.

2.,Prior Art Conventional fuzes may be grouped according to differentactuating characteristics: Briefly,

1. Timing out preset interval required to travel to tara. Mechanicaltiming,

b chemical timing,

c. Electronic timing,.

i. Analogue timing, ii. Digital timing;

2..Detecting proximity of target; and

3. Impacting on target.

Once a conventional timing fuze. has been preset and sent into flight,control by the gunner is lost, and accuracy is subject tounaccounted-for movement of the target and the accuracy of the timingsystem. Once a conventional proximity detecting fuze has been sent intoflight, control by the gunner is lost, and the fuze may be subject topremature detonation by other proximate objects. Once a conventionaltarget impacting fuze is sent into flight, control by the gunner islost.

BRIEF SUMMARY OF THE INVENTION It is an object of this invention toprovide a system having the inherent accuracy of an electronic, digitaltiming actuator plus the ability of the gunner to adjust the interval inflight to actuation, thereby attaining the best characteristics of adigital timer and a proximity fuze.

A feature of this invention, (as shown in FIG. 1) is an electronic,digital, time fuze, whose time base is introduced over a radar commandlink at a rate which is inversely proportional to the desired projectileflight time. A target following ranging device, such as a ranging laser,provides target range information to a pulsed radar transmitter. Therange signal from the ranging device controls a variable pulse ratecontrol unit which in turn adjusts the transmitter pulse rate to a valueinversely proportional to the target range. The transmitter is fixed tothe weapon system and radiates in the direction of the projectile flightpath. Each projectile includes a fuze actuating circuit consisting of anantenna, an r.f. detector, a fixed-set counter and a firing circuit.

At launch, the fuze actuating circuit within each projectile becomesactivated a short distance after departure from the gun muzzle. As theprojectile travels towards its target it receives a series of r.f.pulses at a rate which will just fill the counter when the projectile isat the proper range. The counter within the fuze counts the pulsesreceived during its flight to target. When the fixed-set number has beenaccumulated, the firing circuit detonates the payload. Once the rate atwhich pulses are to be generated is set, as a function of target range,each projectile must travel the same time, and the same range, before itaccumulates the same full count. Thus, by adjusting the pulse ratefrequency (PRF) of the transmitter, the gunner adjusts the range atwhich the payload is detonated.

Some unique advantages of this system are:

l. The system is insensitive to the rate at which projectiles are fired.That is, with either single-shot or burst fire, payload detonation willoccur at the same range.

2. The desired resolution of the detonation range is limited only by thecapacity of the counter within the fuze and the pulse rate of thetransmitter.

3. The detonation range can be automatically adjusted if automatic rangeinformation is available.

4. The detonation range can be intentionally varied while the projectileis in flight to the target.

5. Jamming is difficult since a special transmitter is required tocommunicate with the projectile and the projectile receiving antenna isdirectional aft wards.

A similar system (as shown in FIG. 7) may be utilized to initiate arocket motor in a boosted projectile at a range most appropriate for itsprogrammed trajectory. Projectile muzzle velocity, weapon elevation andtarget range information are processed to provide time-toignition-pointdata which is subsequently translated into a transmitter pulserepetition frequency.

BRIEF DESCRIPTION OF THE DRAWINGS These and other objects, features andadvantages of the invention will be apparent from the followingspecification thereof taken in conjunction with the accompanying drawingin which:

FIG. 1 is a diagram of a controlled range air burst fuze system for ashell incorporating this invention;

FIG. 2 is a side view, partially in cross-section, of a fuze packageaccording to this invention particularly adapted for insertion in theforward end of a small caliber projectile;

FIG. 3 is a block diagram of the electronic circuitry of the fuze ofFIG. 2;

FIG. 4 is an electronic circuit diagram of the fuze of FIG. 2;

FIG. 5 is a block diagram of the electronic circuitry of the resetflip-flop;

FIG. 6 is a plot of projectile range vs. radar pulse repetitionfrequency; and

FIG. 7 is a perspective view, partially in crosssection, of a fuzepackage according to this invention, particularly adapted for insertionin the aft end of a rocket boosted projectile.

THE PREFERRED EMBODIMENT As discussed above with respect to FIG. 1, thepreferred embodiment of the system includes a source of range data, suchas a ranging lasar 10, a variable pulse rate control 12, a pulsetransmitter such as an X-band radar 14, a transmitter antenna 16, aweapon l8, and one or more projectiles 20. Each projectile 20 has a fuze22 which, as seen in FIG. 2, includes a housing 24 containing an antennasuch as a slot antenna 26, electronic circuitry 28, a battery 30, whichmay be a thermal battery, a rotor-detonator assembly 32 and a boostercharge 34.

The rotor-detonator assembly 32 may be of the type shown in US. Pat.Application Ser. No. 804,443 filed Mar. 5, 1969 by R. T. Ziemba.Briefly, the assembly 32 comprises an out of line ball rotor 36 having adetonator charge 38 with a filament 40 and a contact brush 42, and aC-shape spring retainer 44. The rotor is held in the out of line, safedisposition until the projectile, in flight, has developed adequate spinto centrifugally enlarge and enable the spring retainer 44 to pass intoan annular recess 46 in the housing to release the rotor. The rotor thenrotates to axially align its center of gravity and the detonator chargewith the longitudinal axis of the projectile. The rotor is journalled ona transverse axis at 48 to constrain the rotor to rotation within apredetermined longitudinal plane so that the contact 42 wipes throughthis plane.

The thermal battery 30 may be of the type shown in US. Pat. ApplicationSer. No. 695,144 filed Jan. 2, 1968 by R.T. Ziemba. Briefly, the batteryincludes two electrodes spaced apart by a normally solid andnonconductive thermally fusible electrolyte. Thermitic material ismounted in thermally conductive relation with the electrolyte and isignitable by a percussion cap which is disposed between two rigidsurfaces, one of which is a relatively displaceable striker element. Thebattery is normally inactive, until the projectile is subjected to aset-back force on firing, which causes the striker element to percussthe cap, which explodes and actuates the thermitic material, which meltsthe electrolyte to activate the battery. The battery 30 is supported ina cavity in the housing by a forward dielectric ring 50 and an aftdielectric ring 52 and is retained forward by a spring clip 54. Theouter case 56 of the battery serves as the negative contact, and isadapted to be wiped by the detonator contact 42.

The electronic circuitry 28 includes the antenna 26, and a diodedetector 60, a two stage video amplifier 62, a counter 64, a firingcircuit 66, and a reset circuit 68. The antenna consists of a doublefour-port slot antenna, whose dimensions and probe phasing are designedto increase antenna gain to the rear of the projectile. The slotconfiguration, using two diametrically opposed double pairs of adjacentslots, quarter-wave spaced, gives an antenna gain in the aft directionof decibels over a standard dipole. Antenna power is peak-detected withthe hot carrier diode 60, whose output signal is the transmitted PRFenvelope. The signal voltage level at this point is approximately 0.05volt, from a 40 kilowatt (peak) transmitter at a 3,000-meter range. Thedetected pulses are amplified by the twostage amplifier 62 to a leveladequate to drive the counter 64. The counter consists of twelveflip-flop stages in a cascade configuration which provide an input tooutput count ratio of 2 or 2048. Switchover of the last stage isdietected to actuate the output circuit, so only a count of 1,024 isrealized from the counter. When the one-output terminal of the eleventhflip-flop is low, and the zero-output terminal of the twelfth flip-flopis low, the output terminal of the gate 66A will be high, drawingcurrent via the output amplifiers 66B and 66C through the filament 40 ofdetonator charge 38 to actuate the detonator after a finite intervalwhich is a function of time and current.

After the projectile is accelerated out of the weapon and the battery isactuated, the battery requires a finite period of time to reach fulloutput voltage. When a voltage adequate for operating the flip-flops isreached, each of these flip-flops may assume either of its one terminalhigh and zero terminal low, or one terminal low zero terminal highstates. Absent the automatic reset circuit, should the eleventhflip-flop one output terminal be low and the twelfth flip-flop zeroterminal be low the detonator filament 40 will start drawing current.

Detonation would otherwise occur after a period of time. Lesscatastrophic, but not desirable, should any of the flip-flop assume itsone-output high state, the counter will give a short count.

The automatic reset circuit 68 forces each of the counter flip-flop oneoutput terminals to its low state upon the initial provision of power tothe fuze from the battery 30. This reset occurs in less than onemicrosecond, which precludes premature actuation of the detonator. Thereset flip-flop 70, the reset NOR gate 72 and the reset pnp commonemitter driver 74 are used to implement the reset circuit as a raceloop. The reset flipflop 70, as seen in FIG. 5 may be structured as twoNOR gates and 82. The one output terminal 84 of the gate 82 is coupledto one of the input terminals 86 of the gate 80, whose other inputterminal 88 serves as the pulse input-terminal. The zero output terminal90 of the gate 80 is coupled to one of the input terminals 92 of thegate 82, whose other input terminal 94 serves as the reset inputterminal. The zero-output terminal 90 of the flip-flop 70 is coupled toone input terminal 95 of the NOR gate 72, whose other input terminal 96is coupled to ground. The output terminal 98 of the gate is coupled tothe base of the driver 74. The emitter of the driver is coupled to thesupply voltage and the collector is coupled to the reset bus 100. TheNOR gate 72 provides the longest delay in the loop, i.e., the slowestinput to output transfer; and the driver provides the least delay.

The operation of the reset circuit may be broken into three phases, vis:Phase I, the interval during power coming up; Phase II, the intervalafter reset and before receipt of the first transmitter pulse; and PhaseIII, the action on receipt of the first transmitter pulse.

Consider Phase I. The reset flip-flop zero output terminal 90 mayinitially assume either a high or low state. Assume the zero outputterminal 90 is high, then the NOR gate output terminal 98 is initiallyand steady state low, the base electrode is initially and steady statelow, and the driver initially and steady state conducts so that thereset bus 100 is initially and steady state high. The high signal on thereset bus resets all of the counter flip-flops. The high reset signal atinput terminal 94 also provides a low signal at output terminal 84 andthence a low signal at input terminal 86 and thus maintains outputterminal 90 high. Assume the zero output terminal is low, then the NORgate output terminal 98 is initially low, and, because of the longtransfer delay, the base electrode is initially low and the driverinitially conducts so that the reset bus 100 is initially high. Theinitial high signal on the reset bus 100 resets all of the counterflip-flops, and also resets the reset flip. After the long transferdelay the NOR gate output terminal 98 becomeshigh, making the baseelectrode high and turning off the driver so that the reset bus becomeslow. However, the reset flip-flop has already been reset, so that itszero output terminal is now high, and as described previously the driverconducts and the reset bus again becomes high.

Thus, in Phase II, the reset flip-flop zero output terminal is high, theNOR gate output terminal 98 is low, the driver conducts, and the resetbus 100 is high. Also, the reset flip flop one output terminal 84 islow.

When, in Phase III, the first transmitter pulse is received, it iscoupled to the input terminal 94 so that the zero output terminal 90goes low. However, the transmitter pulse is shaped to have a widthgreater than the a the presence of a voltage which might cause ansacci-s dental detonation.

The variable pulse rate features of the transmitting radar isillustrated in FIG. 6 which shows the variation in pulse rate requiredto detonate a fuze payload as a function of target range with a countercapacity of T 1,024 i.e., 2 counts. The pulse rate varies from about10,000 pps at 100 meters to 200 pps at 2,000 meters. At 2,000 meters,fuze detonation resolution is :00] meter. This assumes a constant ratePRF which is the manner in which the radar would normally be operated ina burst fire mode. For single-shot firings the PRF may be programmed toincrease in rate as the projectile travels down range, thereby providinghigher resolution at maximum projectile range.

A SECOND EMBODIMENT As shown in FIG. 7, a fuze embodying this inventionmay be incorporated in a rocket-boosted projectile as an in-flightigniter assembly. The assembly 200 includes a nozzle plug 202, an innerplug 204 supporting a three-turn helical antenna 206 wound on adielectric core 208, a detector assembly 210, and a cannister 2 12. Thecannister includes a thermal battery 214, the counter and resetcircuitry 216, the detonation initiater 218, and the rocket igniter 220.The circuitry is substantially identical to that shown in FIG. 4, withthe substitution of the helical antenna for the slotted antenna.

The counter and reset flip-flops may be 913 elements and the NOR gatesmay be 910 elements as shown in the May 1964 catalogue of FairchildSemiconductor Division of Fairchild Camera and Instrument Corporation.

What is claimed is:

ICA' weapon system comprising:

a projectile having a fuze;

said fuze including a receiving antenna for receiving pulses,

an r.f. detector having an input terminal coupled to said receivingantenna and an output terminal,

a fixed-set counter having a plurality of multistate stages, an inputterminal coupled to said detector output terminal for accumulatingpulses therefrom and an output terminal for presenting a full-countsignal when a preset count of pulses has been accumulated;

a firing circuit having an input terminal coupled to said counter outputterminal for detonating said fuze when said full-count signal ispresented by said counter; and

reset means for automatically forcing each of said stages of saidcounter to a predetermined one of said states.

1. A weapon system comprising: a projectile having a fuze; said fuzeincluding a receiving antenna for receiving pulses, an r.f. detectorhaving an input terminal coupled to said receiving antenna and an outputterminal, a fixed-set counter having a plurality of multi-state stages,an input terminal coupled to said detector output terminal foraccumulating pulses therefrom and an output terminal for presenting afull-count signal when a preset count of pulses has been accumulated; afiring circuit having an input terminal coupled to said counter outputterminal for detonating said fuze when said full-count signal ispresented by said counter; and reset means for automatically forcingeach of said stages of said counter to a predetermined one of saidstates.